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Woodchuck Hibernation

2-2-17-woodchuck-280As fun as it would be to see a Woodchuck on Groundhog Day, it’s not likely to occur in New England, even taking into account climate change, at least not yet. Rather than migrate or remain active and adapt to winter conditions, Woodchucks lower their metabolism and hibernate through the winter.   Their heart rate, body temperature and breathing rate are decreased significantly in order to conserve energy.

One assumes that once a hibernating animal’s metabolism is lowered, it remains lowered for the duration of hibernation. However, it turns out that this is not the case. All of the species of hibernators that have been studied have woken up periodically throughout the winter and warmed themselves up. During these two-three day (on average) arousals, the Woodchuck’s body temperature (roughly 38°F. during hibernation) rises to 98.6°F., its normal temperature during the summer. During these arousal times Woodchucks do not eat. Rather, they rely on deposits of stored body fat, which results in their losing about 40 percent of their body mass by the time green plants are available in the spring. Woodchucks’ bouts of hibernation are initially short, then they lengthen to an average of eight days, and then shorten again as the season progresses.

Arousal consumes a lot of energy (a single arousal may consume as much energy as ten days of hibernation) so it must have a crucial function. Theories regarding this function include restoration of depleted nutrients in the blood, invigoration of immune system, elimination of toxic substances, dealing with potassium loss and facilitation of sperm production in males. As of today, however, the reason for this arousal phenomenon has not been determined.

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4 responses

  1. Very interesting. We learned in our January Four Winds lesson that woodchucks’ heart rate when they’re active is about 130 beats per minute; during hibernation, it slows to 4 beats per minute. The kids were pretty amazed when we clapped out those contrasting rates (as was I)!

    February 2, 2017 at 8:46 am

    • Well, I just read the piece on woodchucks in your “Naturally Curious Day by Day” (which I love!), and see numbers for heart rate that are a bit less extreme: about 100/min when active, down to 15/min when hibernating – still pretty amazing to imagine, and contrast!

      February 2, 2017 at 9:09 am

  2. Kathie Fiveash

    This is so fascinating. When the woodchuck, or bear, or whatever hibernator we are considering, wakes up temporarily, does it stay in the den or actually leave it to wander or forage or whatever? I remember reading that when birds go into torpor at night, there is a possibility that the body will not be able to muster whatever it takes to awaken, so that torpor is a risky business, a fine line, a knife edge.

    February 2, 2017 at 8:48 am

  3. Alice Pratt

    Losing 40% of body fat must make them hungry & maybe grumpy! They don’t set up a pantry?

    February 2, 2017 at 3:28 pm

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